Process for making alloys of magnesium and aluminum



Patented Mar. 29, 1938 UNITED STATES PROCESS FOR MAKING ALLOYS 0F MAG- v NESIUM AND ALUMINUM Alexander Luschenowsky, Berlin, Germany No Drawing. Application November 6, 1935, Se-

rial No. 48,545. 1934 In Germany November 22,

8 Claims. (Cl. 75 -147) The present invention relates to alloys of magnesium and aluminum, and more particularly to .processesfor-the-production of such alloys.

The properties of alloys of magnesium with aluminum depend to a very large extent on whether the said alloys-consist principally of solid solutions and are free from harmful compounds, as also from enclosed particles of the residues of the fluxes. This is true not only in the case of alloys having a preponderating magnesium content, but also in the case of alloys having a preponderating aluminum content. As soon as precipitated intermetallic compounds and chemical compounds such as magnesium'aluminides are present in place of solid solutions, the alloys fail to exhibit the degree of resistance to corrosion aimed at. The mechanical properties of the alloys 'are also dependent on the same factors. Enclosed particles of the constituent, part of the fluxes likewise, lead to decomposition or disintegration of the alloy.

It is already known to subject the melted a1u minum on account of its aflinity to the constituents of the atmosphere to a refining process. Furthermore, in recognition of the fact that impurities of the above-mentioned harmful nature,- even when only present in traces, ofl'er, particularly in the,case of magnesium containing chlorides, points of attack for the corroding media, it has already been'proposed to carry out the alloying of the magnesium 'with aluminum under such conditions as insure the complete removal of non-metallic impurities of the two metals, and also the avoidance of the formation of such; impurities during the alloying process, andin order to attain this end it has been recommended that the alloying of the magnesium should be carried out in the presence of chloride of magnesium or of mixtures of salts which contain in addition to chloride of magnesium which is free from water, thickening means such as fluorides.

The hitherto known processes for the produc-' tion of the alloys in question do not, however, permit of fulfilling the requirements above set forth. w

The alloys. produced according to the said known processes either contain, in addition to solid solutions, .harmful chemical compounds, or they are not-free from'residues' of flux, or again they exhibit these two defects.

- From the .Grube equi1ibrium diagram (Borne mann -Binitre Legierungen) for Mgs-Al. it is seen that the formation'of solid solutions without the simultaneous occurrence of harmful comexothermic reaction.

pounds is only ensured if the proportion of aluminum exceeds that of the magnesium or is about equal to the latter. This requirement is, however, obviously not fulfilled by the known procedure in the alloying of magnesium and aluminum, inasmuchas hitherto it was always customar-y to dissolve solid magnesium in liquid aluminum, as a result of which, one the surface of the slowly melting magnesium, the'proportlon of magnesium was of necessity higher than the proportion of aluminum at this place, so that mixture conditions which operated unfavourably arose locally. On the other hand, itwashitherto necessary to adopt the said alloying process, inasmuch as, on account of its great inflammability, the magnesium could hardly be melted and poured without a fiuxing means. With 'the use of a fiuxing means, however, it would not be possible to prevent particles of the fluxing means from penetrating into the alloy and constituting in the latter harmful enclosed particles causing the decomposition or'disintegration of the alloy.

The new process for alloying magnesium and aluminum, forming-the subject matter of the present invention, is free from the disadvantages above set forth and offers important advantages over the hitherto known processes.

The principal novel feature of the invention. resides in the fact that'for the production of alloys of magnesium and aluminum, a magnesium whichhas been pre-refined by treatment with hydrogen peroxide (H202) or hydrogen per. oxide and hydrogen, and has in particular been freed from oxides, nitrides, chlorides, fluorides and carbon compounds and the 'combustibility of which has been reduced by the pre-refinement,

.is melted without fiuxing means and'is added in the liquid state to the molten aluminum whilst vigorously stirring the melt and causing a violent The new process can be employed even without protection by means of inert gases. It is necessary to employ a magnesium the combustlbllity of which is considerablylowered by suit-' able refinement as aforesaid. It is inter alia possible 'to produce such a grade of magnesiumby thermo-chemical means. The process according to the invention can be carried out with a magnesium producedfby electrolytic means-if the said magnesium is subjected to a suitable refining process; The process according to the invention can be carried out with certainty with every grade of magnesium which has been treated and refined-in the molten condition with hydrocompounds, and containing higher oxygen compounds of manganese, particularly MnaOaor MnOa (for example a flux such as is described in the U. S. A. patent specification No. 1,989,456).

The essence of the process'forming the principal subject matter of the present application resides in the fact that the magnesium of suitable quality, which is obtained by the above described pre-reflnement, is melted, and the melt is added without any protection by fluxing means to the liquid aluminum which is'likewise melted without fluxing means, in such manner as to render it possible with the greatest attainable degree of certainty to avoid a preponderance of the magnesiuin in the melt either temporarily or locally, this resulting from the fact that the liquid magnesium is led into the liquid aluminum melt and is intimately mixed with the latter as quickly as possible by energetic stirring. The exothermic reaction caused by this procedureis perceptible externally by the production of a very considerable increase of temperature. After the temperature increase resulting from the exothermic reaction, the crucible is closed by means of a lid and is allowed to stand for 15 to 20 minutes. Meanwhile a thin froth-like layer is formed which floats on the surface of the melt and contains the magnesium aluminides and the like, as also oxides. The'said layer" can easily be taken of! whereupon the alloy can be poured out. The solidified alloy consists of solid solutions and is almost free from undesired chemical compounds. Naturally enclosed particles from the res'idues'of the fluxing means are also non-existent in th alloy.

Any heavier impurities which may be present become deposited at the bottom of the crucible.

The losses which arise amount to about 8 to 10%. As already mentioned the formation of solid solutions is only ensured when certain definite mixing proportions are employed. For

this reason it is advantageous in the production of magnesium aluminum alloys to prepare in the first place an initial alloy which consists of about 42 to 54% of magnesium; the remaining part being aluminum. The most favourable results are obtained when about 45% of magnesium is mixed with of aluminum. This initial alloy is then employed for the production of the finished alloys having preponderating aluminum content or preponderating magnesium content as the case may be. The said initial alloy is added to the aluminum or the magnesium respectively in such quantities as correspond to the desired composition of the finished alloy. The finished alloys also remain nearly free from harmful compounds.

' As compared with the known processes the novel process according to the invention offers the following important advantages:

The alloys of magnesium and aluminum produced according to the novel process are almost entirely free from harmful compounds and in particular from magnesium aluminides (mag-' nesium silicides can, it is true, not be removed in the manner described). The alloys contain no residues of fluxing materials.- As a result of this the alloys according to the invention are distinguished by substantially increased resistance to corrosion as also by improved mechanic properties-they possess increased tensile strength, higher elastic limit and greater elongation. In consequence of the favourable crystal formation and the absence of harmful magnesiumaluminum-compounds, the alloys are characterized by extremely good flowing qualities in the molten state, which fact greatly facilitates the casting of the alloys. The malleability of the alloys is also increased. The novel process according to the invention is exceptionally suitable 'for the production of all pressed, wrought, rolled and drawn alloys. I

A further advantage resides in the fact that by the aid of the initial alloy produced according to the new process, even small concerns can produce corrosion resistant alloys of high qualitative value with the plant at the disposal of the said concerns. Such concerns can, by the employment of one and the same initial alloy. keep the magnesium content of the final alloy in correspondence with their particular requirements and can in this manner produce alloys, for

example, possessing different hardness and other causes an increase in the tensile strength of the alloys.

I claim:

1. A process for the production of alloys of magnesium and aluminum, comprising in steps:

pre-rei'lning magnesium by treatment in the liquid state with hydrogen peroxide and thereby reducing its combustibility; melting said magnesium without fluxing means; pouring said magnesium in a liquid state into molten aluminum thereby causing an exothermic reaction.

2. A process for the production of alloys of magnesium and aluminum, comprising in steps: pre-refining magnesium by treatment in the liquid state with hydrogen peroxide and thereby freeing it inter alia from oxides, nitrides, chlorides, fluorides and carbon compounds and reducing its combustibility-; melting said magliquid state with hydrogen peroxide and thereby reducing its combustibility; melting said magnesium without fluxing means; introducing said magnesium in a liquid state into molten aluminum thereby causing an exothermic reaction; the proportion of magnesium employed being 42-54% and the remaining percentage of the alloy consisting of the aluminum.

4. A process for the production of alloys of magnesium and aluminum, as specified in claim 3, wherein 45% of magnesium is alloyed with 55% of aluminum.

5. A process for the production of alloys of magnesium an aluminum, as specified in claim 1, wherein the pre-reflning of the magnesium comprises treating the magnesium in the molten condition with hydrogen peroxide (H202) and hydrogen substantially as described.

6. A process for the -production of alloys of magnesium and aluminum, as specified in claim 1, wherein the pre-refining of the magnesium comprises treating the magnesium in the molten condition with hydrogen peroxide (H202), and wherein the melting of the magnesium for the purpose-of the pre-refining is efiected in conjunction with a fluXing means consisting of chlorides and fluorides which contains higher oxygen compounds of manganese, particularly manganese oxide (M11203) and manganese dioxide (MnO2).

7. A process for the production of alloys or magnesium and aluminum, as specified in claim 1, wherein the pre-refining of the magnesium comprises treating the magnesium in the molten condition with hydrogen peroxide (H202) and hydrogen, and wherein the melting of the magnesium for the purpose of the pre-refining is efiected in conjunction with a fluxing means consisting of chlorides and fluorides which contains higher oxygen compounds of manganese, particularly manganese oxide (MnzOa) and manganese dioxide (MnOz).

8. A process for the production of alloys of magnesium and aluminum, comprising in steps: treating magnesium in the molten condition with hydrogen peroxide (H202), and thereby prerefining it so as substantially to free it from oxides, nitrides, chlorides, fluorides and carbon compounds and to reduce its combustibility; introducing the thus pre-refined magnesium in a liquid state in the absence of fluxing means into ALEXANDER LUSCHENOWSKY. 

